Four ways to add a fireplace, and what each one takes

The four types, ranked by scope

The cost to install a fireplace starts with a choice of type, and the type decides how much of the house the job touches. From the lightest to the heaviest:

• Electric: a plug-in or hardwired unit with no combustion and no vent. An electrician runs any new circuit.
• Vented gas: a direct-vent or B-vent unit listed under ANSI Z21.88 or Z21.50, with a vent run to the outside and a gas supply run by a gas contractor.
• Factory-built wood: a UL 127 listed firebox with the listed chimney its manual names, framed into the wall and run through the roof.
• Site-built masonry: a firebox, smoke chamber and chimney built of masonry under FBC Residential R1001 and R1003, on a concrete footing of its own.

Factory-built wood units and the chimney they come with

Factory-built fireplaces are tested as complete systems. FBC Residential R1004.1 requires each one to be listed and labeled, tested to UL 127, and installed to the conditions of its listing. The chimney is part of that system. Under R1005.1, a factory-built chimney has to carry a listing and be installed and terminated as its maker's instructions direct.

R1005.3 holds a factory-built chimney that serves a solid-fuel appliance to the Type HT requirements of UL 103, while one made for an open-combustion-chamber fireplace meets UL 103 without the HT rating, so the fireplace's manual names the exact chimney that goes with it.

That gives the job a fixed parts list: the firebox, chimney sections, firestops where the chimney passes floors and ceilings, any attic shield the manual specifies, roof flashing, the termination cap, and a chase if the chimney runs outside. The scope moves with the chimney's height and route, since each section of pipe and each ceiling it passes adds parts and labor.

Site-built masonry: the largest scope

Masonry is built in place, and its weight needs a foundation of its own. FBC Residential R1001.2 calls for a footing at least 12 inches thick, in concrete or solid masonry, that extends a minimum of 6 inches beyond the face of the fireplace or foundation wall all the way around. On top of that go the firebox, the smoke chamber, the damper, the flue lining and the chimney through the roof.

Each of those parts is a trade task with separate materials and cure times, and the finished stack must reach the height R1003.9 sets. Masonry therefore sits at the top of the scale, and it is the option that changes the structure of the house the most.

Gas and electric: less chimney, more coordination

A vented gas fireplace skips the masonry chimney but still needs a vent. A direct-vent unit pulls its combustion air from outdoors and pushes exhaust out through sealed pipe, and it can terminate at a wall where its manual permits. A B-vent unit burns room air and exhausts vertically through the roof. Route, length and termination clearances follow the manual and the fuel gas code.

The gas supply is separate work. A gas contractor runs the line and connects it, and the estimate shows that as another trade's line. Electric units need no vent or gas, but a hardwired unit or one on a dedicated circuit needs an electrician, and a recessed unit needs a framed opening sized to its manual.

Framing and clearances

Every type except a freestanding electric unit sits in a framed opening, and the framing has to respect the clearances in the unit's listing. For a factory-built unit, the manual gives the clearance from the firebox, the chimney and the top of the opening to any wood, including the header and any mantel you plan to add later.

A wall that is already open, or an outside wall where a chase can be built, is a smaller job than cutting into a finished interior wall or rerouting framing around a new chimney. The estimate names what is cut, what is framed, and who closes and finishes the wall afterward. Firestops where the chimney passes each floor and ceiling, and any attic shield the manual calls for, belong to the framing work, since they hold insulation and wood at the listed distance from the pipe.

The hearth in front of the opening

A wood-burning fireplace has to have a noncombustible hearth extension ahead of its opening. For masonry fireplaces, R1001.10 sets it at 16 inches in front and 8 inches beyond each side, or 20 inches and 12 inches when the opening measures 6 square feet or more. For factory-built units, R1004.2 ties the hearth extension to the unit's listing, and a listed hearth extender complies with UL 1618.

The hearth's finish is a separate choice, and tile, stone or a raised hearth each take a different amount of work. Gas and electric units set their hearth needs in their manuals.

Where the building department comes in

Adding a fireplace is construction inside the house, and state law (F.S. 553.79) requires a permit before a building is built or altered, apart from exempt work. The permit section of the code's administrative chapter (105.1) extends the rule to gas and mechanical system installs.

The building department issues the permit and sets the inspections, and its schedule decides when walls can be closed. Permit time belongs in the plan, so the estimate names the applicant and the inspections to expect.

What moves each type up or down

Within each type, a handful of variables do the moving. These are the ones the estimate is built around:

• Electric: plug-in or hardwired, recessed or wall-hung, and the finish around it.
• Vented gas: the vent route and length, a wall or roof termination, the gas line distance, and power for a blower or remote.
• Factory-built wood: chimney height, the number of ceilings crossed, an inside run or an outside chase, and the hearth.
• Masonry: the footing, chimney height, the flue lining choice, the brick or stone selected, and cure time between stages.

Reading an installation estimate

A useful estimate names the unit and its listing, the chimney or vent parts, the framing and clearances, the hearth, the permit, and every line that belongs to another trade: gas, electrical, drywall and paint. When two quotes for the cost to add a fireplace differ, check first whether they are for the same type and the same route.

A lower number that leaves out the vent termination, the firestops or the permit is not a smaller job. It is an incomplete one.